Chitosan Modifying Nanoscale Zero Valent Iron for Tetracycline Removal from Aqueous Solutions: Proposed Pathway

摘要

For the first time, functionalized zero-valent iron/walnut shell composite (CS-WS-NZVI) was prepared by immobilizing zero-valent iron nanoparticles within walnut shell (WS) modifying with chitosan using liquid phase reduction method. Activity of CS-WS-NZVI was investigated using tetracycline (TC) as target pollutant. Batch experiments were carried out to determinate the effect of reactant concentration, pH value, solution temperature, and competitive anions. Results show that TC could be removed by physical adsorption and chemical reduction on CS-WS-NZVI in a short time with high removal rates (more than 99.02%) at the optimal experiment conditions. Then, scanning electron microscopy analysis reveals that nanoscale zero-valent iron (NZVI) was distributed dispersedly on CS-WS-NZVI without being oxidized, and the mean particle size was 30–100 nm. Characterization results of X-ray diffraction and Fourier transforms infrared spectra of CS-WS-NZVI revealed that the iron nanoparticles were successfully loaded on the surface of WS. LC-MS analysis of the treated solution showed that degradation products were mainly derived from TC after losses of some groups from the ring, and the CS-WS-NZVI can absorb both TC and its degradation products. Furthermore, degradation of TC using CS-WS-NZVI was found to follow the two-parameter pseudo-first order decay kinetics model. Overall, our results indicated that CS-WS-NZVI might be a promising functional material for TC wastewater remediation.